Systems for selectively detonating perforating charges



June 27, 1967 J. W. HARRIGAN, JR

SYSTEM FOR SELECTIVELY DETONATING PERFORATING CHARGES Filed Dec. 22, 1964 2 Sheets-Sheet l I N VEN TOR.

BY k l/ I I 430 7M I M W June 1967 .1. w. HARRIGAN, JR 3,327,791

SYSTEM FOR SELECTIVELY DETONATING PERFORATING CHARGES 2 Sheets-Sheet 2 Filed Dec. 22, 1964 L i Z% J 0/20 14% ficz xvvga/ad/l I INVENTOR.

BY W United States Patent 3,327,791 SYSTEMS FOR SELECTIVELY DETDNATENG PERFORATING CHARGES John W. Harrigan, In, Houston, Tex., assignor, by mesue assignments, to Schlumherger Technology Corporation,

Houston, Tex., a corporation of Texas Filed Dec. 22, 1964, Ser. No. 420,345 17 Claims. (Cl. 1754.55)

ABSTRACT OF THE DHSCLOSURE This disclosure is directed to oil well perforating apparatus having a number of perforating devices such as shaped charges and adapted for suspension from a cable having only two conductors. To detonate individual ones of these shaped charges, each contact on two or more solenoid-actuated, multi-contact selector switches is separately connected to an electrically responsive detonator associated with one or more shaped charges that are to be detonated at one time. By means of appropriately arranged semi-c-onductor diodes and Zener diodes, the selector switches can be selectively actuated to successively connect each of the detonators into the firing circuit one at a time. Then, once a particular detonator is connected into the firing circuit, the detonator is actuated by increasing the voltage applied to the firing circuit.

Accordingly, as will subsequently become apparent, this invention relates to apparatus for detonating explosives for perforating oil wells; and, more particularly, pertains to electrical systems for selectively detonating individual shaped charges in a well-perforating tool.

The present trend in well-perforating techniques is to place only one or, at most, a very few perforations at each of carefully selected points in a well rather than indiscriminately scattering a large number of perforations along a wide interval. To place such small groups or single perforations at various selected depths, apparatus carrying a number of shaped charges is lowered into a well to a particular depth where a perforation is to be placed. Then, the first of these charges is detonated. Thereafter, the apparatus is re-positioned to another depth and another charge is fired. This procedure is repeated until all of the desired perforations have been made.

It will be realized, of course, that where a group of shaped charges are to be individually detonated, each of the charges must have separate detonating means as Well as be isolated from adjacent charges. Accordingly, welldesigned selectively fired shaped charge apparatus is generally comprised of a series of tandemly mounted shaped charges that are suitably isolated from one another within a sealed carrier. Each of these charges has its own electrically initiated blasting cap connected to an electrical control system which is arranged to connect the charges in a predetermined sequence to an electrical source at the surface of the ground. I

A typical electrical control system for such apparatus quite often employs a solenoid-actuated, multi-position selector switch mounted within the shaped charge carrier that is suitably arranged to sequentially connect each of the blasting caps in turn to the electrical source at the surface. Generally, these selector switches include a group of ganged wafers with one of these wafers having a plurality of fixed, circumferentially spaced contacts connected to the shaped charges. These spaced contacts are engaged in turn by a rotatable contact arm that is successively advanced one position at a time by a solenoid-actuated ratchet-and-pawl mechanism. Thus, as the solenoid is alternately energized and de-energized, the rotatable contact arm is successively advanced to connect the shaped charges into the circuit for individual :detonating as desired.

The perforating apparatus must, of course, be suspended in the Well bore from a cable having electrical conductors therein. The usual practice is to employ a socalled monocable having a single electrical conductor enclosed within a conductive armored sheath which serves as the other conductor in the firing circuit. Heretofore, these systems employing a monocable have had an inherent disadvantage, however, that since only a single solenoid-actuated selector switch could be controlled, the number of charges within the apparatus was limited to the number of switch contacts that could be arranged on that size of switch. Since the current trend is toward smaller sizes of well casings, it will be readily appreciated that as perforating apparatus is correspondingly reduced in size to accommodate such smaller casings, the selector switches must also be reduced with a corresponding decrease in the number of available switch positions.

Thus, heretofore, where the number of shaped charges to be selectively fired was greater than the number of available switch positions, it has been necessary to employ multi-conductor suspension cables. Such multi-conductor cables are not preferred, however, since as its diameter increases, the total length of a cable that can be carried on a given size of winch is reduced. Moreover, with multiple conductors, there is always that possibility that an electrical short or incorrect connection may result in perforating at the wrong depth.

It is, therefore, an object of the present invention to provide reliable mistake-proof systems for use with a monocable to selectively arm a plurality of shaped charges in a predetermined sequence.

This and other objects of the present invention are obtained where there are a plurality of electrically actuatable devices in a well tool by connecting one of these devices to a direct current source which will develop a voltage potential of a predetermined magnitude to actuate that device and connect another of these devices to a direct current source by means that conduct electricity to that other device only when the voltage potential applied is greater than that required to actuate the first device.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts perforating apparatus employing the circuitry of the present invention as it will appear Within a well bore;

FIG. 2 schematically illustrates shaped charge perforating apparatus employing electrical circuitry arranged in accordance with the principles of the present invention; and

FIG. 3 shows an alternate embodiment of electrical circuitry also arranged in accordance with the principles of the present invention.

In FIG. 1, a plurality of shaped charge carriers 1042 are tandemly arranged to assemble perforating apparatus 13. The apparatus 13 is dependently suspended from a monocable 14 within a well bore 15. The first of a number of shaped charges (not shown) has just been detonated and has produced a perforation 16 that extends through the well casing 17 and cement 18 into the earth formation 19. The apparatus 13 is now ready to be shifted to another depth within the well bore 15.

Turning now to FIG. 2, a schematic representation is shown of the shaped charge perforating apparatus 13 of FIG. 1 and the monocable 14 which has a single inner electrical conductor 20- and an electrically conductive outer armor sheath 21 as the other electrical conductor. This monocable 21 is, of course, suitably arranged for being spooled in the usual manner from a winch (not shown) adjacent to the well.

A regulated and controlled DC source 22, such as provided by a battery 23 having a potentiometer 24 across it and in series with an ammeter 25 and control switch 26, is connected through a conventionally arranged reversing switch 27 to conductors 26 and 21 at the upper end of the monocable 14. Thus, the operator may select the polarity and voltage potential on either conductor 20, 21 as well as regulate and control the magnitude of the current flow through the conductors.

A plurality of longitudinally spaced shaped charges 28 are mounted within each of the carriers -12 that comprise the perforating apparatus 13. The monocable 14 is securely fastened to the upper end of the perforating apparatus 13 and its outer conductive sheath 21 is electrically connected to the body of the carriers 10-12. The central conductor of the monocable 14 enters the uppermost carrier 12 through a suitable fluid-tight conductor seal 29. Similar conductor seals 30, 31 are also provided to fluidly seal the central conductor 20 where it passes into each of the other carriers 11 and 10.

A separate electrical system A-C is provided in each of the carriers 10-12 for selectively detonating the shaped charges 28 in that carrier. Each of these electrical systems A-C employ a conventional solenoid-actuated selector switch 32 that, once it has ben actuated, responds to sequential energizations to connect a selected number of the shaped charges 28 within that carrier in succession to the central conductor 20 of the mon-ocable 14 so that the charges may be sequentially detonated. These electrical systems A-C are also suitably arranged to be individually actuated as well as to be disconnected as the next successive systems is being initially actuated.

To accomplish these functions, the selector switch 32 in each electrical system A-C has a solenoid-actuated mechanism 33 for rotating in unison separate switch contact arms 34, 35 around a plurality of ganged, rotary switch wafers 36, 37. Although there may be other suitable mechanisms that could be used, the preferred mechanism 33 has a pawl (not shown) that indexes a rotatable ratchet wheel (not shown) one position each time its solenoid 38 is energized and remains in engagement therewith so long as the solenoid is energized. Then, when the solenoid 38 is de-energized, the pawl returns and engages the next tooth on the ratchet wheel. Thus, by successively energizing and re-energizing the solenoid 38, the contact arms 34 and 35 are advanced in unison one position at a time around their respective switch wafers 36 and 37.

The wafer 37 on each selector switch 32 is arranged to sequentially connect shaped charges 28 in turn to the regulated voltage source 22 for subsequent detonation as desired. Accordingly, although only some of the shaped charges 28 within the carriers 10-12 have been shown in FIG. 2, it will be understood that all but the last contact 39 on the switch wafer 37 are separately connected to individual shaped charges 28 within that carrier. Thus, when the solenoid 33 is first energized, the rotatable contact 35 is shifted from its initial starting position (which has no conductor leading therefrom) as depicted in FIG. 2 to the first contact 40 and stops. An electrical circuit is thereby established from the rotatable contact 35 to this first contact 4t), and from there through a conductor 41 to one side of an electrical igniter 42 at the rear of the shaped charge 28 in that carrier that is to be fired first. Separate conductors 43 provide a return path from the opposite side of each igniter 42 through the body of the carriers 10-12 to the monocable sheath 21.

For reasons that will subsequently be apparent, the other wafer 36 of each of the switches 32 has an almost continuous peripheral contact 44. The rotatable contact 34 for water 36 is arranged to be in continuous electrical contact with the peripheral contact 44 at all times, including the initial starting position shown in FIG. 2, until the selector switch 32 has stepped the rotatable contact around the wafer and it is indexed into its final position 45 which is vacant. The rotary contacts 34, 3 5 and their respective wafers 36, 37 are angularly related so that contact 34 will reach the vacant final position 45 at the same time that rotary contact 35 reaches vacant contact 39.

Two oppositely oriented polarity-responsive means, such as semi-conductor diodes 46 and 47, are connected in parallel with one another to the central conductor 20. The opposite side of diode 46 is connected by a conductor 48 to the rotatable contact member 34 of switch wafer 36. In each of the electrical systems B and C, as well as any subsequent system, conduct-or 48 has a voltage-responsive means, such as a Zener diode 49 serially connected therein. Although a Zener such as at 4913 or 49C could be inserted into conductor 48A of system A, it is preferred not to do so for reasons that will subsequently be apparent. The other diode 47 is poled oppositely to diode 46 and is connected by a conductor 59 to the rotatable contact member 35 of switch wafer 37. A conductor 51 connects the peripheral contact 44 to one end of the coil of solenoid 38. The opposite end of the coil of solenoid 38 is returned to the carrier by another conductor 52. A Zener diode 53 connected across the coil of solenoid 38 provides a safety feature that will be subsequently explained as well as a leakage path for the back EMF induced in the coil whenever voltage is removed therefrom.

Thus, it will be appreciated that the sole difference between electrical system A and systems B and C is that it is preferred not to have a Zener diode, such as at 49, in the first system to be activated, system A. In all other respects, however, the first electrical system A as well as those systems, such as at B and C, in all successive carriers are identical and function in the same manner.

Turning now to the operation of the electrical systems A-C. Assume that all selector switches 32 are in their initial starting positions as depicted in FIG. 2 and that the perforating apparatus 13 is now in position Within the well for detonating the first of the shaped charges 28A in carrier 10. The reversing switch 27 at the surface of the ground is first thrown .to the right as viewed in FIG. 2 to connect the negative terminal of the battery 24 to the central conductor 20 of the monocable 14. It will be appreciated, of course, that whenever the central conductor 20 is at a negative potentiahthe polarity orientation of diodes 47 will prevent current from flowing to the switch wafers 37. Although diodes 46 are correctly oriented to pass current whenever the central conductor 20 is positive, should the reversing switch 27 be accidentally thrown to the left, no current can flow through the central conductor so long as the movable contact members 35 remain in their initial vacant positions depicted in FIG. 2.

It will be understood, therefore, that with the reversing switch 27 thrown to the right as viewed in FIG. 2, whenever the control switch 26 is closed, current can initially flow only through the diodes 46 connected to the solenoids 38 of the selector switches 32. The Zener diodes 49B and 49C will block current flow through conductors 48B and 48C, however, so long as the voltage applied to conductor 2!) is no greater than the predetermined threshold or Zener level of each of these Zeners 49B and 490. It will be appreciated that the potentiometer 24 must be advanced in the direction of arrow 54 a sutficient amount to raise the applied negative voltage to the respective Zener level of each of the Zener diodes 49B and 49C and that not until these Zener levels have been reached will current begin flowing in their respective circuits. Thus, so long as the voltage potential applied to central conductor 20 is kept below the Zener levels of Zener diodes 49B and 43C, voltage can be applied only to the solenoid coil 38A of selector switch 32A and selector switches 32B and 32C will remain in their initial inactive positions shown in FIG. 2.

The magnitude of current flow, of course, is directly related to the resistance in the circuit. Thus, since the combined resistance of the conductors 20, 21 of the monocable 14 and coil of the solenoid 38A will always be known and constant, the operator will also know the magnitude of current that will flow whenever the selector switch 32A is being advanced. The ammeter 25 will, of course, indicate the magnitude of current flow at all times and thereby serve as a guide for the operator.

Once the solenoid 38A has been actuated, the movable contacts 34A and 35A are advanced simultaneously from their starting positions. This, of course, brings the movable contact 35A of switch wafer 37A into contact with switch contact 40A. The movable contact members 34A of the switch wafer 36A will similarly be stepped to its second position on the peripheral contact 44A. It will also be recalled that the solenoid mechanism 33A cannot operate to step switch 32A to the next position without first de-energizing the solenoid 33A. Thus, once the switch 32A has been indexed to its first position, the rotatable contacts 34A, 35A can not be further advanced until the voltage has been greatly reduced or interrupted.

When the selector switch 32A has been advanced to its first operating position, it will be seen that conductor 50A is now connected through movable contact member 35A to conductor 41A which is connected to the first of the shaped charges 28A to be detonated. This shaped charge 28A cannot yet be detonated at this time, however, since diode 47A is poled in such a manner to conduct only when there is a positive polarity on central conductor 20.

Accordingly, it will be realized that by throwing the reversing switch 27 to the left, the positive terminal of the battery 23 is then connected to the central conductor 20 of the monocable 14 with only the control switch 26 breaking the circuit. Once this switch 26 is closed, current will flow through diode 47A and detonate the first of the shaped charges 28A. It will be appreciated that the solenoid 38A will be deenergized in this sequence to allow the solenoid mechanism 33A to return and be ready to index the selector switch 32A to its second operating position when the solenoid 38A is again energized.

After the first of the shaped charges 28A has been detonated, the reversing switch 27 is again thrown to the right to re-apply a negative potential to the central conductor 20 to actuate the solenoid mechanism 33A again and step the movable switch members 34A and 35A to their next operative positions. Then, whenever the reversing switch 27 is again switched to re-apply a positive potential to the central conductor 20, the second of the shaped charges 28A is detonated by closing switch 26. Thereafter, successive reversals of the reversing switch 27 will alternately step the selector switch 32A and fire, in turn, the third of the shaped charges 28A as well as the remaining shaped charges (not shown) connected to each of the contacts on switch wafer 37A.

After the selector switch 32A has reached its next-tolast position and the last of the shaped charges 28A has been detonated, the solenoid mechanism 33A is again actuated to index the movable contact members 34A and 35A to their final positions 45A and 39A. The rotatable contact 34A on wafer 36A will now be in the vacant position 45A which breaks the electrical circuit between conductors 48A and 51A leading to the solenoid 38A. Accordingly, it will be appreciated that voltage can no longer be applied to energize solenoid 38A of the selector switch 32A.

The shaped charges 28B in carrier 11 are the next to be detonated. It will be apparent from FIG. 2 that the operation of the electrical system B for sequentially connecting the shaped charges 28B into the firing circuit and subsequently detonating them will be substantially the same as that previously described in detail with respect to the operation of electrical system A. The sole dif- 6 ference will be that the voltage potential applied to the central conductor 20 of the monocable 14 must be greater than that previously used for electrical system A to actuate the solenoid mechanism 33B.

Accordingly, when the potentiometer 24 is advanced in the direction of arrow 54, the voltage potential on central conductor 20 will be proportionately increased, but no current will fiow through Zener diode 459B, however, until the voltage potential has reached the Zener level of that diode. Then, once this predetermined voltage level has been reached, further advancement of potentiometer 24 in the direction of arrow 54 will result in applying a voltage potential to solenoid 38B as current begins to flow through Zener diode 49B. Because of the well-known inherent characteristics of Zener diodes, however, the voltage present at any moment on the coil of the solenoid 38B will be equal to only the difference between the total voltage applied to central conductor 20 less the predetermined Zener level of Zener diode 49B. This, by way of example, should the solenoid 38B require an actuating voltage of 30 volts and the Zener level of Zener diode 49B be 25 volts, a potential of 55 volts must be applied to central conductor 20 in order to obtain the requisite 30 volts for actuating solenoid 38B.

It will be realized, of course, that by selecting Zener diodes 49B and 490 so that the Zener level of Zener 49C is substantially higher than that of Zener 49B, Zener 49B will conduct before Zener 49C. Thus, although a negative voltage is simultaneously applied to both Zeners 49B and 49C, the solenoid 38B of selector switch 32B will be energized before the applied voltage on conductor 20 has reached the Zener level of Zener 49C.

Inasmuch as Zener diodes have a characteristically low internal resistance once they begin con-ducting, the magiitude of current flow through the circuit as the solenoid 38B is being actuated will be substantially the same as that flowing when solenoid 38A was being actuated. Thus, the operator may again use the ammeter 25 as a guide to determine that the solenoid 38B is being actuated.

In the same manner as previously described, once solenoid 383 has been initially actuated, the rotative switch contact 35B will be indexed to its first operative position 40B in preparation for detonation of the shaped charge 283 to be first detonated. Then, in the same manner as already described, reversal of the reversing switch 27 to the left will allow the operator to detonate the first of the shaped charges 28B to be detonated upon closing of switch 26. Then, by again throwing the reversing switch 27 to the right as viewed in FIG. 2, the solenoid 38B will again be actuated to index the rotatable switch contact 32B to its next position. This operation will continue until all of the charges 28B have been detonated and rotatable contact 35B has advanced around wafer 37B and has finally reached the final vacant position 39B. Then, with all of these shaped charges 28B being detonated, it will now be possible to detonate shaped charges 28C in carrier 12.

Here again, the sole difference between electrical systern C and electrical system B is that Zener diode 49C has a high Zener level, being more than that of Zener diode 49B. Accordingly, this will merely require further advancement of the potentiometer 24 in the direction of arrow 54 in order to raise the voltage potential on central conductor 20 to a sufi'iciently high magnitude to exceed the predetermined Zener level of Zener diode 49C and apply sufiicient voltage to actuate solenoid 38C. The operation of electrical system C is otherwise the same as that already described and is believed therefore unnecessary to devote further attention to such a description.

Although it is unnecessary to change the position of the potentiometer 24 once it has been suflieiently advanced to actuate a particular solenoid 38 and to merely reverse switch 27 and, if desired, to open and close switch 26, the potentiometer can also be returned to its original starting position each time. If this is done, the potentiometer 24- must then be advanced in the direction of arrow 54 every time it is desired to actuate a solenoid 38 as well as to detonate shaped charge 28. Moreover, a voltmeter (not shown) can also 'be included in the circuit to provide a further indication for the benefit of the operator.

The Zener diodes 53 across the coils of the solenoids 38 have a predetermined Zener level of only a few volts greater than the voltage necessary to actuate the solenoids 38. This is an added safety feature which pre-.

vents the application of excessive voltage across the coils of the solenoids 38 that might otherwise damage or destroy the coil windings. Thus, should the potentiometer 24 be inadvertently moved too far in the direction of arrow 54, the voltage on conductors 51 will not appreciably exceed the Zener level of Zener diodes 53 without an excessive current. Thus, a positive indication will be provided on meter 25 and those solenoids 28 that are still unactuated will not be prematurely indexed.

Turning now to FIG. 3, perforating apparatus 13' employing an alternate embodiment of electrical circuitry in accordance with the principles of the present invention is shown. Inasmuch as the electrical systems D and E shown in FIG. 3 have many common characteristics with the electrical systems A-C shown in FIG. 2-, it is believed necessary only to describe the ditterences therebetween. The common features are believed to be apparent by comparing FIG. 3 with FIG. 2 and such common features are identified by the same reference numerals with only a prime added or by a suffix D or E.

It will be seen from FIG. 3 that the selector switches 60 differ only from those shown at 32 in FIG. 2 in that switches 60 have only a charge-selector" Wafer 61. Semi-conductor diodes 62 are reversely oriented and connected to the central conductor 20' with one diode being disposed in each of the two carriers 63, 64. Zener diodes 65 are separately connected between each of the diodes 62 and the rotatable contact members 70 of each of the switch wafers 61. The common junction of the diodes 62 and Zeners 64 are joined by a conductor 67 to the coil of the solenoid 68 of their respective selector switch 60.

It will be appreciated, therefore, that by selecting Zener diodes 65 with a Zener level that is greater than the voltage potential required to actuate the solenoids 68, selector switches 60- can be actuated before the voltage applied to central conductor 20" has reached the Zener level of Zeners 65. Furthermore, since, as already described, the indexing mechanisms '69 of selector switches 60 do not return until the solenoids 68 have been de-energized, a continued application of voltage to a solenoid will not cause its selector switch to index to another position so long as the voltage is not reduced. It will be realized also that with the diodes 62 being reversely oriented with respect to one another, when a negative potential is applied to the central conductor 29, only diode 621) will conduct. Similarly, diode 62E will not conduct until a positive potential is applied to the central conductor 20.

Accordingly, to operate the perforating apparatus 13' shown in FIG. 3, the reversing switch 27 is first thrown to the right, for example, where it will remain until all charges 28D in the lowermost carrier 63 have been separately detonated. Then, with selector switch 60D still being in its initial starting position as depicted in FIG. 3, the control switch 26 is closed and the potentiorneter 24' is slowly advanced in the direction of arrow 54 to increase the negative voltage applied to the central conductor 20 to a level suflicient to actuate the solenoid mechanism 69D of the selector switch 69D.

Once the selector switch 60D has been actuated, the rotatable contact 70D is stepped from the position shown in FIG. 3 to the first contact 71D of switch wafer 61D. A conductor 72D leads from contact 71D to the igniter 42D of the shaped charge 28D to be detonated first. The shaped charge 28D connected to contact 71D will not be immediately detonated, however, since so long as the voltage on the central conductor 20 is less than the Zener level of Zener 65D, current can not flow through the Zener to the igniter 42D of the shaped charge. It will be recalled as well that the selector switch 60D can not be indexed again until the voltage has been first reduced. Thus, if he desires, the operator can stop the potentiometer 24 at this intermediate position to delay detonation of the shaped charge 28D.

Once potentiometer 24 is advanced further in the direction of arrow 54, however, the voltage on the central conductor 20' of the monocable 14' will subsequently reach a potential equal to the Zener level of Zener diode 65D. Then, by continuing to increase the applied voltage on the central conductor 29' to a magnitude greater than the Zener level of Zener diode 65D, the shaped charge 28D connected to contact 71D of switch wafer 61D will finally be detonated.

Upon returning the potentiometer 24 to its initial position, the solenoid 68D will be de-energized when the voltage drops to a particular minimum to return the indexing mechanism of selector switch 69D to its initial position. Then, by again advancing the potentiometer 24' in the direction of arrow 54 the rotatable contact 70D will be indexed to its second operative position 73D and connect the next shaped charge 28D into the circuit. A-s already descri'bed, the further advance of potentiometer 24' will again raise the voltage on the central conductor 20 to a level sufiicient to again exceed the Zener level of Zener diode 65D and then detonate the second shaped charge 28D.

Thus, it will be appreciated that as the potentiometer 24 is successively advanced and restored, each of the shaped charges 28D will be sequentially connected into the firing circuit one at a time and then detonated as desired.

When all of the shaped charges 28D in the lowermost carrier 63 have been detonated, it is necessary only for the operator to throw the reversing switch 27 to the left so as to reverse the polarity on the central conductor 20' of the monocable 14. Then, by again successively advancing and returning the potentiometer 24', the shaped charges 28E in carrier 64 will be fired in the same manner as already described.

With the electrical systems D and E as shown in FIG. 3, after a particular shaped charge 289 or 2813. has been detonated, the operator must return the potentiometer 24, to its initial position each time before the selector switch 60 can be indexed to its next position. Thus, by observing the ammeter 25', the operator will be able to watch the current rise as the potentiometer 24' is advanced in the direction of arrow 54'. Initially, the current will rise at a fairly constant rate until the solenoid mechanism 69 indexes the selector switch 60. At the instant this solenoid mechanism 69 is actuated, there will be a momentary but detectable deflection of the pointer of meter 25', which deflection indicates that the solenoid mechanism has operated. Then, as the potentiometer 24' is advanced still further to bring the voltage applied to the central conductor 20' in excess of the Zener level of Zener '65, the current will again rise at a fairly constant rate. When a shaped charge 28D or 28E detonates however, the ammeter 25' will again deflect and then drop-off sharply. This sudden drop-off is, of course, the result of the igniter 42]) opening so that the only resistance remaining in the particular electrical system D or B will 'be that of the coil of the solenoid 68. The current will naturally drop to whatever is being drawn by the coil of the solenoid 68 as it holds the solenoid mechanism 69 engaged in the manner previously described.

Thus, it will be appreciated that these electrical systems D and E depicted in FIG. 3 further serve to give positive indications each time a. solenoid mechanism 69 is actuated as well as each time that a shaped charge 28D or 28B is detonated. As previously described, it is necessary for the potentiometer 24 to be returned to its original position each time to restore the solenoid-actuated mechanism 69 so it may index the selector switch 60 to its next operative position. The same cycle will, of course, occur each time the potentiometer 24' is advanced to first index the selector switch 60 to its next position and then detonate the particular shaped charge 28D or 28E. It will be further appreciated that with the electrical systems D and E the operator has also the option of either actuating control switch 26' each time a shaped charge 28D or 28E is to be detonated or else leaving the switch 26' closed. In the latter event, the only operative manipulations which need be made are the alternate advancements and retrogressions of the potentiometer 24. Thus, if it is desired to perforate a particular formation interval at the same longi tudinal spacing of the shaped charges 28D or 28E, the operator need only position the perforating apparatus 13' at the correct depth and then alternately advance and return the potentiometer 24' until the desired number of shaped charges 28D or 28E have been detonated.

Accordingly, it will be appreciated that the present invention has provided new and improved means for selectively arming and detonating a plurality of shaped charges in a predetermined sequence. Moreover, although the electrical systems disclosed herein are suitable for use with a monocable, the number of shaped charges that can be selectively controlled has been greatly increased to at least twice the number of switch contacts on a particular selector switch.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore, the aim of the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed in:

1. In a Well tool including a carrier and a plurality of electrically-actuatable means in said carrier, means for selectively actuating each electrically actuatable means in a predetermined manner comprising: source means for selectively developing direct current voltage between a first potential and a second greater potential; means for connecting said source means to one of said electrically-actuatable means; and means conductive only in response to a predetermined voltage potential for connecting said source means to another of said electricallyactuatable means, said predetermined voltage potential being intermediate of said first and second source potentials.

2. In a well tool including a carrier adapted for suspension in a well bore by a cable having a pair of electrical conductors and a plurality of electrically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage between a first potential and a second greater potential; means in said carrier for connecting said electrical conductors to one of said electricallyactuatable means; and means in said carrier and conductive only in response to a predetermined voltage potential for connecting said electrical conductors to another of said electrically-actuatable means, said predetermined voltage potential being intermediate of said first and second source potentials.

3. In a Well tool including a carrier and a plurality of electrically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: source means for selectively developing direct current voltage between a first potential and a second greater potential; first means conductive only in response to a first predetermined voltage potential for connecting said source means to one of said electrically-actuatable means; and second means conductive only in response to a second predetermined voltage potential for connecting said source means to another of said electrically-actuatable means, said predetermined voltage potentials being intermediate of said first and second source potentials.

4. In a well tool including a carrier adapted for suspension in a well here by a cable having a pair of electrical conductors and a plurality of electrically-detonatable explosive charge means in said carrier, means for selectively detonating said explosive charge means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage between a first potential and a second greater potential; first means in said carrier and conductive only in response to a first predetermined voltage potential for connecting said electrical conductors to one of said explosive charge means; and second means in said carrier and conductive only in response to a second predetermined voltage potential for connecting said electrical conductors to another of said explosive charge means, said predetermined voltage potentials being intermediate of said first and second source potentials.

5. In a well tool including a carrier and a plurality of electrically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: source means for selectively developing direct current voltage between a first potential and a second greater potential; means for connecting said source means to a first one of said electrically-actuatable means; first means conductive only in response to a first predetermined voltage potential intermediate of said first and second source potentials for connecting said source means to a second one of said electrically-actuatable means; and second means conductive only in response to a second predetermined voltage potential intermediate of said first and second source potentials for connecting said source means to a third one of said electrically-actuatable means, said second predetermined voltage potential being greater than said first predetermined voltage potential.

6. In a well tool including a carrier adapted for suspension in a well bore by a cable having a pair of electrical conductors, and first, second and third groups of electzically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage between a first potential and a second greater potential; first, second and third means in said carrier for respectively connecting individual ones of said first, second and third groups of electrically-actuata'ble means in sequence to said conductors, each of said connecting means including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions connected to separate ones of said electrically-actuatable means and electricallyresponsive actuating means for sequentially indexing said movable contact toindividual ones of said operative positions in response to successive energizations thereof; first means for connecting said first actuating means to said conductors; second means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials for connecting said second actuating means to said conductors; and third means conductive only in response to a predetermined voltage potential intermediate said first and second source potentials for connecting said third actuating means to said conductors.

7. In a well tool including a carrier adapted for suspension in a well bore by a cable having a pair of electrical conductors and first, second and third groups of electrically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage of opposite polarities between a first potential and a second greater potential; first, second and third means in said carrier for respectively connecting individual ones of said first, second and third groups of electrically-actuatable means in sequence to said conductors, each of said connecting means including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions connected to separate ones of said electrically-actuatable means, electrically-responsive actuating means for sequentially indexing said movable contact to individual ones of said operative positions in response to successive energizations thereof and a first unidirectional conductor means connecting said common contact to said conductors and poled in a first direction for applying voltage of one polarity to said common contact; a plurality of second unidirectional conductor means respectively connected to each of said actuating means and poled in a second direction for applying voltage of the opposite polarity to said switch-actuating means; first means for connecting said second unidirectional conductor means of said first actuating means to said conductors; second means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials for connecting said second unidirectional conductor means of said second actuating means to said conductors; and third means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials for connecting said second unidirectional conductor means of said third actuating means to said conductors.

8. In a well tool including a carrier adapted for suspension in a well bore by a cable having a pair of electrical conductors and first, second and third groups of electrically detonatable explosive charge means in said carrier, means for selectively detonating said explosive charge means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage of opposite polarities between a first potential and a second greater potential; first and second unidirectional conductor means connected to one of said conductors and poled in opposite directions; first, second and third means in said carrier for respectively connecting to said first unidirectional conductor means individual ones of 7 said first, second and third groups of explosive charge means in sequence, each of said connecting means including multiple-position switching means having a common contact connected to said first unidirectional conductor means and movable from a normal disconnected position to a plurality of operative positions connected to separate ones of said explosive charge means and electrically-responsive actuating means for sequentially index ing said movable contact to individual ones of said operative positions in response to successive energizations thereof; first means for connecting said unidirectional conductor means to said first actuating means; second means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials for connecting said second unidirectional conductor means to said second actuating means; and third means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials for connecting said second unidirectional conductor means to said third actuating means.

9. In a well tool including a carrier adapted for suspension in a well bore by a cable having a pair of electrical conductors and first, second and third groups of electrically de-tonatable explosive charge means in said carrier, means for selectively detonating said explosive charge means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage of opposite polarities between a first potential and a second greater potential; first and second unidirectional conductor means connected to one of said conductors and poled in opposite directions; first, second and third means in said carrier for respectively connecting to said first unidirectional conductor means individual ones of said first, second and third groups of explosive charge means in sequence, each of said connecting means including multiple-position switching means having a first common contact connected to said first unidirectional conductor means and movable from a normal disconnected initial position to a plurality of spaced operative positions connected to separate ones of said explosive charge means, a second common contact movable from a plurality of interconnected positions to a final disconnected position and electrically-responsive actuating means for sequentially indexing said movable contacts in unison to their respective positions in response to successive energizations thereof, said actuating means being connected to said interconnected switch positions; first means for connecting said second unidirectional conductor means to said second common contact of said first switching means; second means conductive only in response to a first predetermined voltage potential intermediate of said first and second source potentials for connecting said second unidirectional conductor means to said second common contact of said second switching means; and third means conductive only in response to a second predetermined voltage potential diiierent from said first predetermined voltage potential and intermediate of said first and second source potentials for connecting said second unidirectional conductor means to said common contact of said third switching means.

10. As a subcombination: a housing sub having a plurality of electrically-detonatable explosive charge means therein; means for connecting individual ones of said explosive charge means in a predetermined sequence including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions; electricallyresponsive actuating means for sequentially indexing said movable common contact to individual ones of said operative positions in response to successive energizations thereof; and diode means connected to said actuating means and conductive only in response to direct current voltage in excess of a predetermined potential for energizing said actuating means.

11. As a subcombination: a housing sub having a plurality of electrically-detonatable explosive charge means therein; means for connecting individual ones of said explosive charge means in a predetermined sequence including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions; electricallyresponsive actuating means for sequentially indexing said movable common contact to individual ones of said operative positions in response to successive energizations thereof; first unidirectional conductor means connected to said common contact, said first unidirectional conductor means being poled in one direction and adapted for connection to a source of direct current; means connected to said actuating means and conductive only in response to direct current voltage in excess of a predetermined potential for energizing said actuating means; and second unidirectional conductormeans connected to said voltage-responsive means, said second unidirectional conductor means being poled in the opposite direction from said first unidirectional conductor means and adapted for connection to a source of direct current.

12. As a subcombination: a housing having a plurality of electrically-detonatable explosive charge means therein;

first and second unidirectional conductor means poled in opposite directions and adapted for connection to a source of direct current; means for connecting to said first unidirectional conductor means individual ones of said explosive charge means in sequence including multipleposition switching means having a first common contact connected to said first unidirectional conductor means and movable across a plurality of spaced switch positions connected to separate ones of said explosive charge means, a second common contact movable across a plurality of interconected switch positions and electrically responsive actuating means for sequentially indexing said movable contacts in unison to their respective positions in response to successive energizations thereof, said actuating means being connected to said interconnected switch positions; and means conductive only in response to direct current voltage in excess of a predetermined potential for connecting said second unidirectional conductor means to said second common contact.

13. In a well tool including a carrier and a plurality of electrically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: source means for selectively developing direct current voltage between a first potential and a second greater voltage potential; first means conductive only in response to a first predetermined voltage of one polarity and having a potential intermediate of said first and second source potentials for connecting said source means to another of said electricallyactuatable means; and second means conductive only in response to a second predetermined voltage of the opposite polarity and having a potential intermediate of said first and second source potentials for connecting said source means to another of said electrically-actuatable means, said predetermined voltage potentials being substantially equal.

14. In a well tool including a carrier adapted for suspension in a well bore by a cable having a pair of electrical conductors and first and second groups of electrically-actuatable means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising: surface-located source means connected to said electrical conductors for selectively developing direct current voltage between a first potential and a second greater potential; first and second means in said carrier for respectively connecting individual ones of said first and second groups of electricallyactuatable means in sequence to said conductors, each of said connecting means including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions connected to separate ones of said electricallyactuatable means and electrically-responsive actuating means for sequentially indexing said movable contact to individual ones of said operative positions in response to successive energizations thereof; first and second means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials for connecting said common contacts to one of said conductors; and means in said carrier for connecting said actuating means to said conductors.

15. In a well tool including a carrier adapted for suspension in a Well bore by a cable having a pair of electrical conductors and first and second groups of electrically-actuatabe means in said carrier, means for selectively actuating said electrically-actuatable means in a predetermined manner comprising; surface-located source means connected to said electrical conductors for selectively developing direct current voltage of opposite polarities between a first potential and a second greater potential; first and second unidirectional conductor means connected to one of said conductors and poled in opposite directions; and first and second means in said carrier for respectively connecting to said uniconductor means individual ones of said first and second groups of electricallyactuatable means in sequence, each of said connecting means including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions, connected to separate ones of said electrically-actuatable means, electrically-responsive actuating means for sequentially indexing said movable contact to individual ones of said operative positions in response to successive energizations thereof, means conductive only in response to a predetermined voltage potential intermediate of said first and second source potentials connecting said com mon contact to the respective one of said uniconductor means, and conductor means for connecting said actuating means to the respective one of said uniconductor means.

16. As a subcombination: a housing sub having a plurality of electrically-detonatable explosive charge means therein; means for connecting individual ones of said explosive charge means in a predetermined sequence including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions; electricallyresponsive actuating means for sequentially indexing said movable common contact to individual ones of said operative positions in response to successive energizations thereof; and diode means connected to said common contact and conductive only in response to direct current voltage in excess of a predetermined potential.

17. As a subcombination: a housing sub having a plurality of electrically-detonatable explosive charge means therein; means for connecting individual ones of said explosive charge means in a predetermined sequence including multiple-position switching means having a common contact movable from a normal disconnected position to a plurality of operative positions; electricallyresponsive actuating means for sequentially indexing said movable common contact to individual ones of said operative positions in response to successive energizations thereof; means connected to said common contact and conductive only in response to direct current voltage in excess of a predetermined potential; and unidirectional conductor means connected to said voltage-responsive means and said actuating means and adapted for connection to a source of direct current.

References Cited UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner. JACOB L. NACKENOFF, Examiner. D. H. BROWN, Assistant Examiner. 

1. IN A WELL TOOL INCLUDING A CARRIER AND A PLURALITY OF ELECTRICALLY-ACTUATABLE MEANS IN SAID CARRIER, MEANS FOR SELECTIVELY ACTUATING EACH ELECTRICALLY ACTUATABLE MEANS IN A PREDETERMINED MANNER COMPRISING: SOURCE MEANS FOR SELECTIVELY DEVELOPING DIRECT CURRENT VOLTAGE BETWEEN A FIRST POTENTIAL AND A SECOND GREATER POTENTIAL; MEANS FOR CONNECTING SAID SOURCE MEANS TO ONE OF SAID ELECTRICALLY-ACTUATABLE MEANS; AND MEANS CONDUCTIVE ONLY IN RESPONSE TO A PREDETERMINED VOLTAGE POTENTIAL FOR CONNECTING SAID SOURCE MEANS TO ANOTHER OF SAID ELECTRICALLYACTUATABLE MEANS, SAID PREDETERMINED VOLTAGE POTENTIAL 